''Hexagonaria'' is a genus of colonial rugose coral. Fossils are found in rock formations dating to the

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

period, about 350 million years ago. Specimens of ''Hexagonaria'' can be found in most of the rock formations of the Traverse Group in

Michigan Michigan () is a state in the Great Lakes region of the upper Midwestern United States. With a population of nearly 10.12 million and an area of nearly , Michigan is the 10th-largest state by population, the 11th-largest by area, and the ...

. Fossils of this genus form Petoskey stones, the

state stone Leaders of states in the U.S. which have significant mineral deposits often create a state mineral, rock, stone or gemstone to promote interest in their natural resources, history, tourism, etc. Not every state has an official state mineral, rock, ...

of Michigan. They can be seen and found in most Midwestern states. ''Hexagonaria'' is a common constituent of the coral reefs exposed in Devonian Fossil Gorge below the

Coralville Lake Coralville Lake is an artificial lake in Johnson County, Iowa, United States, formed by the Coralville Dam, a dam built from 1949 to 1958 on the Iowa River upstream from the city of Coralville, Iowa. History After widespread flooding in the Unit ...

spillway and in many exposures of the Coralville Formation in the vicinity of Coralville, Iowa.Brian J. Witzke and Bill J. Bunker, Sedimentation and stratigraphic architecture of a Middle Devonian (late Givetian) transgressive-regressive carbonate-evaporite cycle, Coralville Formation, Iowa area
Paleozoic Sequence Stratigraphy, Biostratrigraphy and Biogeology, Special Paper 321
Geological Society of America, 1997.

Species Identification

Based on Erwin C. Strumm's ''Corals of the Traverse Group of Michigan Part 13, Hexagonaria'', published in 1970.

Image Gallery

Image:Fossil Hexagonaria mirabilis MHNL.jpg, ''Hexagonaria mirabilis'' Image:Unpolished Petoskey Stone (Photo by John Mortimore).jpg, ''H. percarinata'', " Petoskey stone"

Species Identification

Image Gallery

References

Further reading